I saw something that said the reason the universe exists is that everything exists, in an infinite multiverse. This then answers why the laws of physics of our universe are the way they are, which is that they are one of an infinite set picked by chance, and removes the arbitrariness of our existence. However the idea of everything existing is hard for me to even begin to comprehend, and it seems like there might be some paradoxes that arise from it. To be clear I am asking if the concept of "everything" is logically coherent.
Is the concept of "everything" logically coherent?
I would say largely yes, but within the framework of your views on ontology. Therefore, your "everything" and someone else's "everything" may not agree with the definition.
I saw something that said the reason the universe exists is that everything exists, in an infinite multiverse.
Yes, there are many claims to why the universe exists. The scientific study of the origin of the universe is known as cosmogony. Of course, there are non-scientific explanations too. Origin myths are nearly universal in the mythologies of the world, and creation myths seem to serve a psychological purpose. So, when you start talking with certainty about the origins of the universe, you are more likely than not to be engaged in the metaphysical speculation. From the standpoint of empirical evidence, claims about the origin of the physical universe are largely those made in regard to the Big Bang theory. The Multiverse hypothesis is somewhat controversial in that such discussions seem to be largely non- or pseudo-scientific. Remember, creation myths seem to important psychologically regardless of their actual veracity. My personal views are solidly with physicist Sabine Hossenfelder who claims that multiverse theories are religions, not scientific theories. What is everything? What is the universe? There is much philosophical contention over everything that exists because it is not agreed upon what "to exist" means.
But let's talk language. First and foremost, the idea of "everything" is a linguistic artifact. Utterances are nothing more than elements of sound production. Propositions like definitions are conceptual representations, building blocks of meanings, the study of which is known as semantics. How can one define everything? Well, in a naive sense, just like MW:
Definition of everything
1a : all that exists
b : all that relates to the subject
2 : all that is important you mean everything to me
3 : all sorts of other things —used to indicate related but unspecified events, facts, or conditions
Right away, the 1a leads us to the most philosophical sense, "all that exists", which then devolves into a discussion about "existence" and hence why ontological discourse is important (and dare we say exists?) Since there are posts about existence on this site, we won't rehash, however, we can give a few pointers to philosophers who are well regarded in metaontological circles.
First, there is Aristotle whose works are voluminous. Aristotle is not the only Ancient Greek of repute, but he is rather indisputably the most influential by way of the Scholastics domination of philosophy during the growth of the Catholic Church which accoring to WP:
The Catholic Church, also known as the Roman Catholic Church, is the largest Christian church, with 1.3 billion baptised Catholics worldwide as of 2019.4 As the world's oldest and largest continuously functioning international institution,8 it has played a prominent role in the history and development of Western civilisation.
Aristotle, however, came after Plato. Plato is tremendously significant because of his theory of Forms. As a mathematical constuctivist, I personally rail against Platonic thinking, however, no reasonable thinker can doubt the power of the idea, and the way it continues to captivate philosophical thinkers.
I would include Immanuel Kant because he is often considered as the progenitor of modern philosophy and is a father both to analytical and Contintental philosophy. Kant challenged the nature of "existence" when he spoke of what are now known as Kantian forms (Britannica) and advocated the thing-in-itself.
More contemporaneously are the Austrian Meinong to whom the phrase Meinong's jungle refers. Meinong was influential because he systematically attempted to make sense of non-physical referents. According to WP:
The Meinongian theory of objects (Gegenstandstheorie) was influential in the debate over sense and reference between Gottlob Frege and Bertrand Russell which led to the establishment of analytic philosophy and contemporary philosophy of language. Russell's theory of descriptions, in the words of P. M. S. Hacker, enables him to "thin out the luxuriant Meinongian jungle of entities (such as the round square), which, it had appeared, must in some sense subsist in order to be talked about".3 According to the theory of descriptions, speakers are not committed to asserting the existence of referents for the names they use.
Rudolf Carnap is seminal because of his position among the logical positivists, who in analytical circles, who collectively were tremendously influential philosophical thinkers when it came to science. Carnap's approach to existence was very much about eliminating grand metaphysical speculation, and attempting to reduce existence to observation, particularly the scientific kind.
And lastly, I'd include Quine, who is larger than life when it comes to contributions in logic and philosophy and influenced a generation of thinkers with his views on existence and the naturalized epistemology.
Now, what I would argue is that the linguistic device known as "everything" is essentially a psycological operation of the mind in a way that the antipsychologists would have decried. In the philosophy of mathematics, foundational to understanding math is set theory, and in set theory we have the notion of the domain of discourse, the union operation, and the universal set. It is natural for the mind to identify the existence of things, then to differentiate and keep count of things. Subitization is built into the brain.
So, is "everything" logical? Yes, given your logic which determines what does and doesn't exist, and your system of keeping track of individual things. Whether that system is the one proposed by Plato, Meinong, or Quine is another matter entirely.
Firstly, we don’t know that there’s an infinite multiverse. If there is then the probability of any given thing existing approximates to 1 but mutually contradictory things can’t exist in the same frame of reference. For example, an irresistible force could exist and an immovable object could exist but they couldn’t have the same frame of reference. In everyday terms you could have a force that can move anything north or south and an object that couldn’t be moved east or west. So if you want an irresistible force and an immovable object then you can have both but only in such a way that they can never meet.
To the question, "What is there?" Quine 'famously' replied, "Everything." And I think Russell spoke of the robustness of existence, as something that ruled out things that 'there are some of' that, yet, don't exist.
But the fact that unrestricted quantification is relatively uncommon is no reason to doubt it is attainable in certain contexts. Unfortunately, many philosophers have recently doubted that genuinely unrestricted quantification is even coherent, much less attainable.21
21For examples, the reader may consult Dummett 1991; Fine 2006; Glanzberg 2004; Hellman 2006; Lavine 2006; and Parsons 2006.
Quine's set theory has a universal set, but so resistance to talk of a universal set is a motivating factor in at least some rejection of unrestricted quantification.
No, because you've misunderstood and misrepresented the concept
A multiverse doesn't mean "everything can exist". It means that universes can exist with all possible values of underlying basic physical constants. The maths shows (apparently; this isn't my field) that for many possible values of those constants, the result would be that universe ceasing to exist very quickly. Only certain ranges of values give stable universes.
That doesn't mean everything will exist though. Changing basic physical properties doesn't mean you've made anything particular happen.
To find out what is everything we must first ascertain what is a thing? You must question your own epistemology. Are you naturalist or are you a supernaturalist? This has great bearing on what you consider to be a thing. Do you allow for extant immaterial things? God is immaterial but to Christians he is still a thing. God is not nothing.
For some people in the scientific community the idea of a thing being immaterial and in existence is far beyond anything there worldview could ever consider possible. Do you allow for something that exist in a way that is not bound to our physical universe?
These are the questions you are starting your philosophical journey with. Enjoy your journey you are about to start questioning every cherished belief a person can have.
Your question, like many others posted on this and similar forums, is one which boils down to the intended meaning of words. What do you mean by everything? If you mean everything that exists, then the answer to your question is trivially yes by definition. If by everything you mean something other than everything that exists, then you need to define what else is encompassed by your definition and you need to define the assumptions that are to be made to distinguish between possible things and impossible things. As things stand what you see to me asking is whether an undefined set of things can exist given an undefined set of criteria that determine whether their existence is possible, and unsurprisingly that is unanswerable.
Could everything exist?
Logically speaking, possibly. But if everything is that which is existing then the statement is just a tautology: a thing is that which exists, so it follows that all things are necessarily existing. By this, I don't mean its existence is necessary, it could be contingent.
To get out of this tautology we need to broaden what we mean by existing. It could mean everything that has ever existed. In which case the answer is no. There are no dinosaurs on earth. They don't exist.
But they could conceivably exist, say for example we could find a full genetic code for a dinosaur and we had the technology to 'engineer' such an animal from its code. But whilst we might be able to resurrect an extinct genus or an extinct species, we cannot resurrect a specific individual of that species. Take Genghis Khan, even were we to build him, it would not be him. A person is much more than his genetic code. He is also his world, his culture, and his language.
However, the world you are considering is much larger. It is all conceivable worlds as modeled by our physical laws. This again, though, is not everything possible. Unfortunately, it's a highly speculative idea with very little chance to no chance of ever being proven, even in principle. But it's very dramatic, which is why everyone knows about it.
Apparently, late medieval theologians contemplated how many angels could dance on the head of a pin. A hundred? A thousand? A million? It's a byword in wasting time debating nonsense today. Likewise, one could ask certain modern physicists how many universes can you fit into a multiverse? A trillion, a gadzillion, a googleplex - maybe even aleph one - with probably just as much eventual sense (ie. nonsense).
Preface: I am not a physicist, and I am not your physicist, this does not constitute advice on the current state of accepted physical understanding, but then again you are asking a question where scientific understanding boils down to "well according to this equation" and various arguments of logical viewpoints. In other words, these are extrapolated concepts that arise from people really good at maths having a lot of time on their hands, and not the normal kind of numbers math, the kind with symbols that denote the truthiness of 2 being greater than 1. The ideas expressed from these exercises are not necessarily real physical observable testable and quantifiable. At the absolute minimum, not yet at least, if ever. More likely it's a bunch of smart people musing on existence, and the media ran with it for sensationalized clickbait. On to your question, and adding my 2 cents viewpoint to your already full plate of information to digest (I hope you saved room for dessert)...
If we are to take the definition of the multiverse to mean every possibility playing out an atoms width away from each other, or in a separate bubble universe next to our own, in my mind there does exist a few logical issues however those logical issues do have a resolution, unfortunately, a potentially depressing and yet readily endearing one.
Supposing there are an infinite number of potential universes where any possible concept could play out, there could be a universe where we're all Spider-Man, or we are all comic books, or we are all made of cheese, or butter, or diamond, or where 2+2=5 because 2s happen to represent an extremely large value of 2 there, or where we exist as the evolution of the dinosaurs instead of the proto tree shrew. And if an infinite number of possibilities exist than an infinite number of those infinite possibilities must also exist, an infinite number of infinite universes. But here's where it all falls down, for an infinite number of thing exists universes there must also be an infinite thing that does not exist universes, essentially polar opposites, concept and anti-concept. And an infinite number of those Infinities. These infinite infinities would cancel out against each other, the infinite cheese universes would cancel out against the infinite not cheese universes. All of the potentiality crashes out of possibility. Summing out to a null. What remains after this cancellation of the infinity of infinite possibilities are the tiny perturbations between them. The little incalculably small, random chance, even if you knew the location, velocity, and energy state of each bit of mass from whatever beginning they burst forth from to right this moment these wibbles would still surprise you....the inequalities in the equation. We exist in and of what can't be canceled out. This place is what is left over after everything that could possibly ever be is obliterated from potentiality by the never would have been.
We are the remainder of an unbalanced equation reconciling an infinite infinities collapsing against each other, crashing out of potentiality.
Some may see that as depressing. I prefer to see it as pretty freaking amazing! Lucky us there wasn't an anti-fleshy-pinkish-primate universe, eh? This gives us a chance to explore this....odd lump of randomness set before us by whatever forgot to carry that 2 a few (many) billion years ago. There is a massive bubble of stuff out there, right here, for us to explore, and even though it's basically made of the same handful of stuff, the sheer amount of places and configurations will keep us quiet busy for a long while. If we don't blow ourselves to hell first. If we can just make it to one more evolutionary jump, a moral one, where we inherently as a species, like horses knowing how to run right from the womb, come to abhor anything other than the absolute last resort protective acts violence, arrogant hatred, the denial of peoples humanity based on entirely arbitrary concepts like genetic expression of pigmentation in skin cells, or where ones parents may have birthed them, as if such things are of their control and could have any meaningful bearing on who that person will be (consider, a psychopath isn't inherently a danger, just a bit of a prick, generally speaking. Plenty of us...er I mean them, operate in society just fine, even tend to do 'the humane thing' in the heat of a snap decision moment. Yes, individual development is a complex messy subject, but do you really think you'd be an entirely different person if you were born at that other major hospital across town?). If we could learn to not take things personally off the bat, if we could learn to seek an understanding of others lifepaths and what has lead them to their views, particularly without the internal adversarial threat of learning something about someone must mean my views change, or worse that knowledge changing my views being a slight against me... If we could simply stop being dicks to each other in the interest of respecting our inherently human rights freedoms and liberties as we would expect ours to be respected in a responsible civil manner, we might actually make it to all the corners of this bubble and see whats sticking to its shell... Though, I call dibs on the infinite cheese bubble... Mmmmmmm, cheese......
This is the true nature of the universe, as plausible as anything else. In this essay I will....